1. Field of the Invention
The present invention relates to a shock absorbing apparatus provided in a positioning apparatus, such as moving-guiding alignment apparatuses of electron beam drawing equipment, precision measurement equipment, and the like, in which high-speed movement and precise positioning are repeated, or scanning movement is precisely performed in a non-atmospheric ambience, for example. The present invention further relates to an apparatus, such as an exposure apparatus, incorporating such a shock absorbing apparatus.
2. Description of the Related Background Art
FIG. 13 is a plan view illustrating an X-Y stage of a conventional positioning apparatus. FIG. 14 is an end view of FIG. 13. In FIGS. 13 and 14, there are shown a base surface plate 501, an X-direction movement substrate 502, and a Y-direction movement substrate 503. A guide member 504 for guiding the X-direction movement substrate 502 along the X-direction of a first alignment direction is provided on the base substrate 501, and a guide member 505 for guiding the Y-direction movement substrate 503 along the Y-direction of a second alignment direction is provided on the X-direction movement substrate 502. A guide block member 506 movable along the guide member 504 is provided on the bottom surface of the X-direction movement substrate 502, and a guide block member 507 movable along the guide member 505 is provided on the bottom surface of the Y-direction movement substrate 503. An overhead plate member 509 for mounting thereto a chucking apparatus for supporting a sample, or the like is provided on the Y-direction movement substrate 503, and reflective mirrors 510 and 511 for position measurement are mounted to the overhead plate member 509. Shock absorbers (shock absorbing apparatuses) 512 are disposed, through a mounting member 513, at places corresponding to stroke ends of the X-direction movement substrate 502 on the base surface plate 501, respectively. Other shock absorbers (shock absorbing apparatuses) 512 are likewise disposed, through a mounting member 514, at places corresponding to stroke ends of the Y-direction movement substrate 503 on the X-direction movement substrate 502, respectively.
Further, Japanese Patent Laid-Open Application No. 10(1998)-340938 discloses an apparatus in which a shock absorber is used in a driving system for a conveyance arm contained in a vacuum chamber. In this apparatus, a driving mechanism for rotating and ascending or descending a cassette surface plate for mounting thereon a wafer cassette in a load-lock chamber is provided, and the driving mechanism is comprised of a rotary actuator and a cassette elevator, and is installed in a housing outside the load-lock chamber. A bellows is provided around the driving axis of the driving mechanism such that a gas-tight condition can be maintained during the movement in the axial direction. The shock absorber for absorbing shock during operation for positioning at a descending end portion of the cassette elevator is provided thereat.
In the conventional apparatus as illustrated in FIGS. 13 and 14, however, when the X-Y stage is situated in the vacuum chamber, it is difficult to readily obtain a compact and light-weight shock absorber which is a vacuum-adapted shock absorbing apparatus. Further, where a bellows member is used to construct a fully enclosed cover for the shock absorber, a compact design is difficult, and the size of a stage apparatus is likely to increase, incurring a large-sized vacuum chamber and large-sized accompanying equipment such as a vacuum pump. The cost of the apparatus is also likely to increase. Furthermore, it takes a long time to exhaust the large-sized vacuum chamber to a desired level of pressure, and a long time is needed to perform its maintenance and so forth. Its productivity is hence lowered. Additionally, if the shock absorber operates repeatedly, fluid in the shock absorber threatens to leak into the chamber.
On the other hand, the apparatus of the above-noted Japanese reference solves such problems (i.e., problems of the increase in size, and the fear of leaks) by placing the shock absorber outside the vacuum chamber. In this apparatus, however, a highly-rigid delivery system is difficult to construct, and since the bellows is provided around the driving axis to keep a gas-tight condition during the operation of driving in the axial direction, external disturbing factors are liable to be transmitted through the bellows to an object to be positioned.